Continuously operating screw machine for the treatment of plastic masses

ABSTRACT

A continuously operating, preferably single screw shaft, multiple-thread screw machine for the treatment, such as, for example, kneading, mixing and homogenizing, of plastic masses with a housing surrounding the screw shaft. The kneading, mixing and homogenizing treatment is carried out by the repeated and controlled separation and recombination of the stream of material. The separation and recombination is accomplished by a screw provided with cross webs in the individual screw channels and longitudinal webs on the outer periphery of the screw threads. The outer edges of the longitudinal webs are spaced from the inner wall of the housing at a greater distance than the clearance of the screw threads with respect to the inner wall of the housing. In addition, the longitudinal webs and cross webs have a flat rising slope of about between 15* to 30* in the direction of rotation of the screw.

United States Patent Koch et al.

[ Aug. 29, 1972 [54] CONTINUOUSLY OPERATING SCREW MACHINE FOR THETREATMENT OF PLASTIC MASSES [72] Inventors: Heinz Koch, Ludwigsburg;Eugen Martin Viihringer, Bietigheim, both of Germany [73] Assignee:Firma Werner 8: Pileiderer, Feuerbach, Germany [22] Filed: Dec. 19, 1969[21] Appl. No.: 886,571

[30] Foreign Application Priority Data Dec. 21, 1968 Germany ..P 18 16440.4

[52] US. Cl. ..259/l09, 107/14 C, 18/12 SM [51] Int. Cl. ..B0lf 7/02Field of Search ..259/1 10, 109, 108, 9, 10, 99, 259/103, 25, 26, 45,46, 68, 69, 104, 4-8, 16, 21-24, 32-34, 40-44, 64-67; 107/14 C, 14

FOREIGN PATENTS OR APPLICATIONS 560,204 9/ 1957 Belgium ..259/ 109Primary Examiner-Jordan Franklin Assistant Examiner-Geo. V. LarkinAttorney-Craig, Antonelli and Hill [57 ABSTRACT A continuouslyoperating, preferably single screw shaft, multiple-thread screw machinefor the treatment, such as, for example, kneading, mixing andhomogenizing, of plastic masses with a housing surrounding the screwshaft. The kneading, mixing and homogenizing treatment is carried out bythe repeated and controlled separation and recombination of the streamof material. The separation and recombination is accomplished by a screwprovided with cross webs in the individual screw channels andlongitudinal webs on the outer periphery of the screw threads. The outeredges of the longitudinal webs are spaced from the inner wall of thehousing at a greater distance than the clearance of the screw threadswith respect to the inner wall of the housing. In addition, thelongitudinal webs and cross webs have a flat rising slope of aboutbetween 15 to 30 in the direction of rotation of the screw.

44Claims,6DrawingFigures Paten ted Aug. 29, 1972 3,687,423

6 Sheets-Sheet l Inventors.-

N MARTIN YOHRINGER FHforn 'S Patented Aug. 29, 1972 6 Sheets-Sheet 2Fig. 2

n'szuz K001! and EuGL-N MARTIN Patented Aug. 29, 1972 6 Sheets-Sheet 5lnrepfagsz 1nd E uGEN MARTIN \wukI' lvER; 57 46 MQM HEINZ. KOCH fInvent-@115: EN MARTIN van/2r CONTINUOUSLY OPERATING SCREW MACHINE FORTHE TREATMENT OF PLASTIC MASSES BACKGROUND OF THE INVENTIONhomogenizing, of plastic masses and being provided with a housingsurrounding the screw shaft.

A conventional screw machine is known which has two auger shaftscooperating as a pair and the screw channels of which are provided withcross webs so that individual chambers are produced in the screwchannels. Between these successive chambers, there remains a certainspatial communication in the longitudinal direction of these chambersdue to these cross webs. This has the purpose of providing an especiallyhigh degree of uniformity of the product mixture. Although it ispossible by means of such cross webs to cause, in each screw channel ofthe screw shaft, material of the stream of material to be transferred inlayers into the subsequent chamber, the thus-combined portions move, ineach case, side-by-side in a more or less loose arrangement withoutactually obtaining an intimate mixing also within smaller volume ranges.

As a result thereof, it can be seen that a really optimum mixing effectcannot be expected in these screw machines by the use of cross websalone. This conclusion' has also been confirmed in practice. Indeed,especially in the processing of viscid or viscous plastic masses (highlyviscous masses), satisfactory results could not be achieved with knownscrew machines.

SUMMARY OF THE INVENTION It is the aim of the present invention toovercome the problems and disadvantages in the previously known screwmachines. A major objective is to provide a continuously operating screwmachine which ensures that kneading, mixing and homogenizing of, inparticular, plastic masses, and also within smaller volume ranges, canbe carried out with especially good results. In contrast to theabove-mentioned conventional twin-shaft screw machine, it is an objectof the present invention to achieve a far higher quality of the treatedmaterial in a single shaft machine. Although the expenditure in machineparts is lower, the quantitative output obtained is not in any wayreduced.

The underlying problems are solved in accordance with the presentinvention by utilizing the essential concept of conducting a mixing,kneading, and homogenizing of the material to be treated in accordancewith the principle of a repeated, controlled separation andrecombination of the stream of material by means of an appropriatelyshaped screw.

Accordingly, the present invention resides mainly in that, in machinesof the above-mentioned type, there are provided, on the one hand, crosswebs in the individual screw channels and, on the other hand,longitudinal webs on the outer periphery of the screw threads, the outeredges of which are disposed at a spacing'from the inner wall of thehousing. The spacing is larger than the running clearance of the screwwindings or threads with respect to the inner wall of the housing. Inthis connection, a conventional multiplethread screw is employed.

The cross web in a screw channel brings about an accumulation of thematerial to be treated with a highly effective shearing action, whereasthe longitudinal web, in conjunction with this accumulation process,provides that a partial stream of the material to be treated can passover into the adjacent screw channel.

Prior to each renewed separation of the stream of material, thepreviously combined partial streams are subjected together to an intenseshearing and kneading treatment. Preferably, the arrangement can be suchthat, in each case, a cross web and a longitudinal web form an anglewith a common vertex. In this connection, the aforementioned webarrangement represents a stream-dividing node.

At the cross web of such a stream-dividing or flowseparating node, thestream of material is accumulated, and the adjacent longitudinal web isdisposed in the irnmediate area of this zone of accumulation, so that apartial stream of the material to be treated is forced to pass from theoriginal screw channel into the adjacent screw channel at thislongitudinal web of the stream dividing node. Precisely by the repeatedcombination and subsequent division of the partial streams, an intimateintermixing is effected even in the smallest volume ranges.

The mixing, kneading, or homogenizing process is even more intensifiedby providing, in each screw channel, stream-dividing nodes consisting ofa cross web and a longitudinal web. It was also found that the manner ofdistributing the cross webs in the individual adjacent screw channelswith respect to the position of the stream-dividing nodes is of specialimportance.

Consequently, the arrangement can also preferably be such that thestream-dividing nodes of adjacent screw channels are disposed offsetwith respect to one another in the conveying direction of the screw, andthat .the end of the cross web of one stream-dividing node is connectedwith the beginning of the longitudinal web of the stream-dividing nodedisposed, offset with respect to the former node in the conveyingdirection, in the adjacent screw channel by means of a continuous screwthread. In this connection, it is possible to arrange one or moreadditional cross webs in the area of this screw thread connecting thestream-dividing nodes.

It is further advisable to provide that one or more additional crosswebsare arranged between two streamdividing nodes, respectively, in thesame screw channel.

It can readily be seen that the result of the mixing, kneading, orhomogenizing process must be improved as more cross webs or longitudinalwebs must be overcome by the material to be treated. Consequently, it ispossible in accordance with the present invention to dispose additionalcross webs preferably between respectively two stream-dividing nodes inthe same screw channel.

In addition to the features of the invention set out above, the presentinvention is aimed at solving a further problem. having very essentialsignificance. Starting with the consideration that the individual massparticle in the stream of material can traverse varying paths within thescrew machine due to successively executed stream divisions andrecombinations, it is of particular value to provide that each massparticle, in-

dependently of the respectively traversed path within the screw machine,must always pass over the same number of longitudinal webs and crosswebs. In this way, it is possible to achieve a treatment during themixing, kneading, and homogenizing which is indeed entirely uniform evenin case of any small volume proportion.

To solve this special problem, the accomplishment has been made inaccordance with the present invention to develop a mathematicalinterrelationship wherein it is naturally also important, in order to beable to render a generally applicable teaching, how many threads thescrew has in each case, and how the transition from the feed zonedisposed in front of the shearing zone provided with stream-dividingnodes is designed. In this connection, in the following remarks, thenumber of threads of the screw is denoted by n, the succession of thesethreads with stream-dividing nodes is designated by kl, k2, k3, etc.,and the number of cross webs being additionally employed is called 2.

In order to facilitate the passage of the stream of material over thelongitudinal webs or the cross webs, these webs can be formed, in allembodiments of the screw configuration, with a flat rising slope ofbetween approximately and 30 in the direction of rotatio of the screw.

BRIEF DESCRIPTION OF THE DRAWING These and further features, advantagesand objects of the present invention will become more apparent from thefollowing description when taken in conjunction with the accompanyingdrawing which shows, for purposes of illustration only, severalembodiments in accordance with the present invention, and wherein:

- FIG. 1 is a partial view of a screw constructed in accordance with thepresent invention and showing the screw in a three-dimensional manner,

FIG. 2 shows one possibility of a design for the cross webs,

FIG. 3 is a partial view of a screw constructed according to the presentinvention with the surface thereof in the form of a developedprojection,

FIG. 4 is a fragmentary view of a developed projection of the screwsurface having a design in accordance with a modification of the presentinvention, and

FIGS. 5 and 6 are developed projections of further modified variants.

DETAILED DESCRIPTION OF THE DRAWING Referring now to the drawings and,in particular to FIG. 1, a single shaft screw of a screw machine havingfour screw channels I, II, III and IV is shown. These screw channels areseparated by the threads of the screws denoted by the numeral 2. In thescrew channels I through IV, cross webs 3 and 3a are provided.

Longitudinal webs are formed by sections of the screw thread havingportions cut away so that the radially outermost edges thereof have alarger spacing from the housing than the outermost edges of theremaining sections of the threads. These longitudinal webs aredesignated by numeral 2a. The distance of the outer edge of thelongitudinal webs 2a and the cross webs 3, 3a from the inner. wall ofthe screw housing 14 is designated by numeral 13 and is larger than therunning clearance which usually .exists between the screw and thehousing. The longitudinal webs 2a and the cross webs 3a are angularlyjoined and have a common vertex 4a. Such a web arrangement consisting ofa longitudinal web 2a and an associated cross web 3a is called astream-dividing node. In FIG. 1, three stream-dividing nodes 1, 1a, 1bcan be seen.

Respectively, two cooperating stream-dividing nodes follow each other inthe conveying direction, as shown by arrow A, of the screw in such amanner that there is disposed, between the end of the cross web 3a ofthe first stream-dividing node 1a and the beginning of the longitudinalweb 2a of the second node lb disposed in the adjacent channel, anuninterrupted web portion, which thus does not have a distributing orspreading effect. This uninterrupted portion is the screw thread portion20. In this case, each web or web portion 2a, 3, 3a having a shearing,kneading, and distributing effect is followed, in the circumferentialdirection, by the screw thread 2 or 20 which does not have adistributing efi'ect. As is customary, these screw threads have aconveying action.

In this embodiment with a quadruple-thread screw, an additional crossweb 3 is provided between respectively two nodes following each other ina channel. Small arrows illustrated in the screw indicate how therepeated, controlled division and combination of the stream of materialis, for example, executed.

It can be seen from FIG. 2 how the cross webs 3, 3a are designed, forexample, with respect to their orientation to the surrounding housing14, for instance how the shearing gaps can be formed. The gap width 13resulting in this case amounts, for example, to between 0.5 and severalmillimeters, depending on the material to be processed and other processconditions. In the direction of screw rotation, as shown by arrow B, thecross webs 3, 3a are designed with a flat ascending slope 15 of about 15to 30. This ascension is to be adapted to the frictional conditions ofthe processed mass. The longitudinal webs 2a can also be designed in asimilar manner.

In FIG. 3, as well as in the following figures, fragmentary sections ofscrews according to the present invention are illustrated, but thesurface thereof is illustrated as a developed projection. FIG. 1 conveysan impression of how the developed projections shown in the followingfigures are to be pictured three-dimensionally.

In FIGS. 3 and 4, the feed and transition zones pertaining to the screware disposed in front of the shearing zone proper and are likewiseillustrated in a developed projection. The feed zone is denoted by 4 andthe transition zone by 5 in FIG. 3. The feed zone 10 in FIG. 4 isprovided with less threads than the subsequent zones, so that themachine can always be operated in the partially filled condition,independently .of the metering.

FIG. 3 is a three-thread screw, i.e. n 3, and thus the number of theadditional cross webs between the nodes 21, 22 is in each case n-l, i.e.3 l 2. The nodes of adjacent screw channels are connected in each caseby screw thread sections and are indicated in sequences F by dot-dashlines. The number of these successions is likewise n-l, i.e. 3 l 2. Inthe transition zone 5, in front of the shearing zone, k-l additionalcross webs 23 and 24 can be seen in front of each first node of the k'"thread (wherein 1 e k E n). Therefore, this means the following.Designating the first channel wherein, as seen in the conveyingdirection A, the first node 21 is disposed, by k and the additionalchannels by k and k then no additional cross web is provided in front ofthe first node 21 in the channel k because at that point k l, i.e. l 1,equals zero. In channels k and k a number of additional cross webs 23and 24 of2 l l, and 3 l 2 respectively, is obtained, which cross websare disposed in front of the respectively first nodes 25 or 22 of thechannels k and k respectively.

FIG. 4 illustrates another successful embodiment of the presentinvention. Here, the stream-dividing nodes are disposed in the form ofseveral groups G of nodes arranged on a common periphery, indicated bydotdash lines. The groups are axially offset with respect to one anotherin the conveying direction A of the screw. Between respectively twonodes 26, 27 following each other in a channel 8, two groups 28, 29 ofadditional cross webs 3 are arranged. These two groups 28, 29 ofadditional cross webs together contain the odd number of z cross webs,in this case 3. One group 28 is disposed in front of the node 30arranged in the next channel 9, as seen in the conveying direction ofthe screw; the other group 29 is disposed, as seen in the conveyingdirection of the screw, after the node 30. The first-mentioned groupcontains cross web. The node 30, in front of which the group 28 isarranged with (z H2) cross webs, is connected, from the point of itsorigin, .with the end of the first node 26 of the two nodes 26, 27following each other in the same channel 8, by means of anon-distributing, or continuous screw thread portion 20.

The transition zone 11 from the feed zone to the shearing :zone is of adifferent configuration in the screw of FIG. 4 than in the previouslydescribed modification of the invention. For this screw has the evennumber of threads n in its shearing zone, in this case 4. The feed zone10 of the machine has the thread number (rt/2) (i.e., 2) for the abovereasons. In the transition zone 11, each second channel of the shearingzone is fed with the material by way of the first node disposed, in theconveying direction, in the next channel rather than being fed directly.For example, the

this case 1, are arranged when the number of the cross webs disposedbetween two nodes following each other in the same channel is equal toz, in this case 3.

The lower limits of the residence time of a mass particle of thematerial to be treated are obtained in the present invention byconsidering that the mass particle under consideration always passes theright-hand shearing web half of each stream-dividing node and thustraverses the shortest path, whereas the upper limits are obtained byconsidering that the mass particle under consideration always passes theleft-hand shearing web half of each stream-dividing node and thustraverses the longest path. Thereby, the width of the residence timespectrum is defined. In spite of the fact that the various massparticles are provided with the possibilities for remaining fordifferent lengths of times, the present invention ensures that each massparticle is subjected to the same treatment in the screw machine by thefact that it must always pass over the same number of longitudinal websand cross webs.

In FIG. 5 as also in the following FIG. 6, it is shown that theconstruction of the present invention additionally anticipates a numberof special cases. The two modifications illustrated in this connectionare offered merely as examples.

FIG. 5 represents only a fragmentary view of a developed projection of ascrew surface and shows that the screw threads 2 in the projection canalso appear in a bent configuration, such a construction likewise beingembraced by the concept of the present invention. In FIG. 5, theextension of the threads is indicated,

in one case, with dot-dash lines. The bends are in each case denoted bynumeral 18. Of course, this construction likewise has stream-dividingnodes 1 and additional cross webs 3 as described above. This specialcase of the construction of the present invention has been chosen inFIG. 5 in order to be able to accommodate more stream-dividing nodesalong the same length of a thread. The more stream-dividing nodes whichcan be accommodated along the same screw length or shearing zone lengthof the screw, the larger becomes the width of the residence timespectrum.

FIG. 6 represents an embodiment quite similar to the one describedabove. Here again, the course of the screw threads 2 is denoted bydot-dash lines, and the bend is denoted by numeral 18. In the specialcase of the construction of the present invention illustrated in FIG. 6,the cross webs of the stream-dividing nodes 1 are combined with theadditional cross webs 3 or groups of these additional cross webs, aspresent in the previously described examples of the invention, thusobtaining the configurations 12. Such a construction permits the maximumnumber possible of stream-dividing nodes along an equally long screwlength.

While we have shown and described several embodiments in accordance withthe present invention, it

should be clear that the same is susceptible of numerous changes andmodifications as will be apparent to a person skilled in the art, andwe, therefore, do not wish to be limited to the details shown anddescribed herein but intend to cover all such changes and modificationsas are encompassed by the scope of the present lnvention.

We claim:

l. Continuously operating screw machine for the treatment, such askneading, mixing and homogenizing,

of plastic masses, comprising: a housing; at least one screw shaft meansoperatively associated with and surrounded by said housing; said screwshaft means having multiple threads defining screw channelstherebetween; cross webs located in said screw channels; andlongitudinal webs located adjacent the outer periphery of said threadsof said screw shaft means, said cross webs and said longitudinal webshaving a larger clearance with respect to internal walls of said housingthan the outer periphery of the threads of said screw shaft means,wherein each of said screw channels, respectively one of said cross websand one of said longitudinal webs constitute a stream-dividing node.

2. Screw machine according to claim 1, wherein said longitudinal websare formed by sections of respective screw threads having the outermostportions cut away so that the outermost edges of these sections have alarger spacing from the housing than the remaining portions of thethreads.

3. Screw machine according to claim 1, wherein respectively one of saidcross webs and one of said longitudinal webs form an angle therebetweenand have a common vertex constituting the stream-dividing node.

4. Screw machine according to claim 1, wherein the outer edges of saidlongitudinal webs are spaced from the inner wall of said housing and thespacing therebetween being larger than the clearance of said threadswith respect to the inner wall of said housing.

5. Screw machine according to claim 3, wherein the outer edges of saidlongitudinal webs are spaced from the inner wall of said housing and thespacing therebetween being larger than the clearance of saidthreads withrespect to the inner wall of said housing.

6. Screw machine according to claim 2, wherein the stream-dividing nodesof adjacent screw channels are offset with respect to each other in theconveying direction of said screw shaft means.

7. Screw machine according to claim 6, wherein an end portion of a crossweb of one stream-dividing node is operatively connected, by means of acontinuous thread portion, to a beginning portion of a longitudinal webof the stream-dividing node offset with respect thereto in the conveyingdirection in the adjacent screw channel.

8. Screw machine according to claim 7, wherein each of said onerespective cross web and longitudinal web constitutes thestream-dividing node by forming an angle therebetween with a commonvertex.

9. Screw machine according to claim 7, wherein at least one cross web islocated in the zone of said continuous thread portion connecting theoffset streamdividing nodes.

l0. Screw machineaccording to claim 9, wherein each of said onerespective cross web and longitudinal web constitutes thestream-dividing node by forming an angle therebetween with a commonvertex,

1 1. Screw machine according to claim 6, wherein at least one cross webis located between two streamdividing nodes in the same screw channel.

12. Screw machine according to claim 11, wherein an end portion of across web of one stream-dividing node is operatively connected, by meansof a continuous thread portion, to a beginning portion of a longitudinalweb of the stream-dividing node offset with respect thereto in theconveying direction in the adjacent screw channel.

13. Screw machine according to claim 12, wherein each of said onerespective cross web and longitudinal web constitutes thestream-dividing node by forming an angle therebetween with a commonvertex.

l4. Screw machine according to claim 7, wherein n number of threads areprovided at said screw shaft means, and n-l additional cross webs areprovided in the zone of said continuous thread portion connecting twostream-dividing nodes offset in the conveying direction and related toadjacent screw channels.

15. Screw machine according to claim 14, wherein a feed zone and atransition zone are provided at said screw shaft means, thestream-dividing nodes connected by said continuous thread portion beingarranged in nl sequences, and k-l additional cross webs being providedat the transition between said feed and transition zones in front ofeach first stream-dividing node of a kth thread, wherein l g k g n.

16. Screw machine according to claim 15, wherein at least onecross webis located between two streamdividing nodes in the same screw channel.

17. Screw machine according to claim 7, wherein an even number n ofthreads are provided and the streamdividing nodes are arranged inparallel groups respectively arranged on a common cross-sectional plane.

18. Screw machine according to claim 17, wherein an odd number z ofadditional cross webs are provided between two stream-dividing nodeslocated in the same screw channel, and wherein (z H2) of the additionalcross webs are in the zone of said. continuous thread portion and theremaining (z l/2) additional cross webs are located after thestream-dividing node following said continuous thread portion, as seenin the conveying direction.

l9. Screw machine according to claim 15, wherein each of said onerespective cross web and longitudinal web constitutes by stream-dividingnode by forming an angle therebetween with a common vertex.

20. Screw machine according to claim 19, wherein at least one cross webis located in the zone of said continuous thread portion connecting theoffset streamdividing nodes. I

21. Screw machine according to claim 19, wherein at least one cross webis located between two streamdividing nodes in the same screw channel.

22. Screw machine according to claim 17, wherein a shearing zone and afeeding zone located forwardly of said shearing zone are provided atsaid screw shaft means and (rt/2) threads are provided at said feedingzone, and wherein two threads of said shearing zone are associated withone thread of said feeding zone.

23. Screw machine according to claim 22, wherein (z l/2) additionalcross webs are provided in the channel of the stream-dividing nodes ofasecond of said parallel groups of the nodes located in across-sectional plane axially between the first and the second of saidparallel groups.

24. Screw machine according to claim 23, wherein each of said onerespective cross web and longitudinal web constitutes thestream-dividing node by forming an angle therebetween with a commonvertex.

25. Screw machine according to claim 24, wherein an odd number z ofadditional cross webs are provided between two stream-dividing nodeslocated in the same screw channel, and wherein (z 'tl/2) of theadditional cross webs are in the zone of said continuous thread portionand the remaining (z 1/2) additional cross webs are located after thestream-dividing node following said continuous thread portion, as seenin the conveying direction.

26. Screw machine according to claim 25, wherein at least one cross webis located in the zone of said continuous thread portion connecting theoffset streamdividing nodes.

27. Screw machine according to claim 25, wherein at least one cross webis located between two streamdividing nodes in the same screw channel.

28. Screw machine according to claim 1, wherein said threads have bentportions at the stream-dividing nodes.

29. Screw machine according to claim 28, wherein the outer edges of saidlongitudinal webs are spaced from the inner wall of said housing and thespacing therebetween being larger than the clearance of said threadswith respect to the inner wall of said housing.

30. Screw machine according to claim 29, wherein each of said onerespective cross web and longitudinal web constitutes thestream-dividing node by forming an angle therebetween with a commonvertex.

31. Screw machine according to claim 30, wherein the stream-dividingnodes of adjacent screw channels are offset with respect to each otherin the conveying direction of said screw shaft means.

32. Screw machine according to claim 31, wherein an end portion of across web of one stream-dividing node is operatively connected, by meansof a continuous thread portion, to a beginning portion of a longitudinalweb of the stream-dividing node offset with respect thereto in theconveying direction in the adjacent screw channel.

33. Screw machine according to claim 32, wherein at least one cross webis located in the zone of said continuous thread portion connecting theoffset streamdividing nodes.

34. Screw machine according to claim 31, wherein at least one cross webis located between two streamdividing nodes in the same screw channel.

35. Screw machine according to claim 31, wherein an even number n ofthreads is provided and the stream-dividing nodes are arranged inparallel groups respectively arranged on a common cross-sectional plane.

36. Screw machine according to claim 1, wherein said longitudinal websand said cross webs are provided with a substantially flat ascendingslope of between about 15 to 37. Screw machine according to claim 36,wherein the outer edges of said longitudinal webs are spaced from theinner wall of said housing and the spacing therebetween being largerthan the clearance of said threads with respect to the inner wall ofsaid housing.

38. Screw machine according to claim 37, wherein respectively one ofsaid cross webs and one of said longitudinal webs form an angletherebetween and have a common vertex thereby constituting thestream-dividingnode.

9. Screw machine according to claim 38, wherein the stream-dividingnodes of adjacent screw channels are offset with respect to each otherin the conveying direction of said screw shaft means.

40. Screw machine according to claim 39, wherein an end portion of across web of one stream-dividing node is operatively connected, by meansof a continuous thread portion, to a beginning portion of a longitudinalweb of the stream-dividing node offset with respect thereto in theconveying direction in the ad- 30 jacent screw channel.

41. Screw machine according to claim 40, wherein at least one cross webis located in the zone of said continuous thread portion connecting theoffset streamdividing nodes.

42. Screw machine according to claim 38, wherein at least one cross webis located between two streamdividing nodes in the same screw channel.

43. Screw machine according to claim 39, wherein n number of threads areprovided at said screw shaft means, and n-1 additional cross webs areprovided in the zone of said continuous thread portion connecting twostream-dividing nodes offset in the conveying direction and related toadjacent screw channels.

44. Screw machine according to claim 37, wherein said threads have bentportions at the stream-dividing nodes.

1. Continuously operating screw machine for the treatment, such as kneading, mixing and homogenizing, of plastic masses, comprising: a housing; at least one screw shaft means operatively associated with and surrounded by said housing; said screw shaft means having multiple threads defining screw channels therebetween; cross webs located in said screw channels; and longitudinal webs located adjacent the outer periphery of said threads of said screw shaft means, said cross webs and said longitudinal webs having a larger clearance with respect to internal walls of said housing than the outer periphery of the threads of said screw shaft means, wherein each of said screw channels, respectively one of said cross webs and one of said longitudinal webs constitute a stream-dividing node.
 2. Screw machine according to claim 1, wherein said longitudinal webs are formed by sections of respective screw threads having the outermost portions cut away so that the outermost edges of these sections have a larger spacing from the housing than the remaining portions of the threads.
 3. Screw machine according to claim 1, wherein respectively one of said cross webs and one of said longitudinal webs form an angle therebetween and have a common vertex constituting the stream-dividing node.
 4. Screw machine according to claim 1, wherein the outer edges of said longitudinal webs are spaced from the inner wall of said housing and the spacing therebetween being larger than the clearance of said threads with respect to the inner wall of said housing.
 5. Screw machine according to claim 3, wherein the outer edges of said longitudinal webs are spaced from the inner wall of said housing and the spacing therebetween being larger than the clearance of said threads with respect to the inner wall of said housing.
 6. Screw machine according to claim 2, wherein the stream-dividing nodes of adjacent screw channels are offset with respect to each other in the conveying direction of said screw shaft means.
 7. Screw machine according to claim 6, wherein an end portion of a cross web of one stream-dividing node is operatively connected, by means of a continuous thread portion, to a beginning portion of a longitudinal web of the stream-dividing node offset with respect thereto in the conveying direction in the adjacent screw channel.
 8. Screw machine accorDing to claim 7, wherein each of said one respective cross web and longitudinal web constitutes the stream-dividing node by forming an angle therebetween with a common vertex.
 9. Screw machine according to claim 7, wherein at least one cross web is located in the zone of said continuous thread portion connecting the offset stream-dividing nodes.
 10. Screw machine according to claim 9, wherein each of said one respective cross web and longitudinal web constitutes the stream-dividing node by forming an angle therebetween with a common vertex.
 11. Screw machine according to claim 6, wherein at least one cross web is located between two stream-dividing nodes in the same screw channel.
 12. Screw machine according to claim 11, wherein an end portion of a cross web of one stream-dividing node is operatively connected, by means of a continuous thread portion, to a beginning portion of a longitudinal web of the stream-dividing node offset with respect thereto in the conveying direction in the adjacent screw channel.
 13. Screw machine according to claim 12, wherein each of said one respective cross web and longitudinal web constitutes the stream-dividing node by forming an angle therebetween with a common vertex.
 14. Screw machine according to claim 7, wherein n number of threads are provided at said screw shaft means, and n-1 additional cross webs are provided in the zone of said continuous thread portion connecting two stream-dividing nodes offset in the conveying direction and related to adjacent screw channels.
 15. Screw machine according to claim 14, wherein a feed zone and a transition zone are provided at said screw shaft means, the stream-dividing nodes connected by said continuous thread portion being arranged in n-1 sequences, and k-1 additional cross webs being provided at the transition between said feed and transition zones in front of each first stream-dividing node of a kth thread, wherein 1 < or = k < or = n.
 16. Screw machine according to claim 15, wherein at least one cross web is located between two stream-dividing nodes in the same screw channel.
 17. Screw machine according to claim 7, wherein an even number n of threads are provided and the stream-dividing nodes are arranged in parallel groups respectively arranged on a common cross-sectional plane.
 18. Screw machine according to claim 17, wherein an odd number z of additional cross webs are provided between two stream-dividing nodes located in the same screw channel, and wherein (z + 1/2) of the additional cross webs are in the zone of said continuous thread portion and the remaining (z - 1/2) additional cross webs are located after the stream-dividing node following said continuous thread portion, as seen in the conveying direction.
 19. Screw machine according to claim 15, wherein each of said one respective cross web and longitudinal web constitutes by stream-dividing node by forming an angle therebetween with a common vertex.
 20. Screw machine according to claim 19, wherein at least one cross web is located in the zone of said continuous thread portion connecting the offset stream-dividing nodes.
 21. Screw machine according to claim 19, wherein at least one cross web is located between two stream-dividing nodes in the same screw channel.
 22. Screw machine according to claim 17, wherein a shearing zone and a feeding zone located forwardly of said shearing zone are provided at said screw shaft means and (n/2) threads are provided at said feeding zone, and wherein two threads of said shearing zone are associated with one thread of said feeding zone.
 23. Screw machine according to claim 22, wherein (z - 1/2) additional cross webs are provided in the channel of the stream-dividing nodes of a second of said parallel groups of the nodes located in a cross-sectional plane axially between the first and the second of said parallel groups.
 24. Screw machine aCcording to claim 23, wherein each of said one respective cross web and longitudinal web constitutes the stream-dividing node by forming an angle therebetween with a common vertex.
 25. Screw machine according to claim 24, wherein an odd number z of additional cross webs are provided between two stream-dividing nodes located in the same screw channel, and wherein (z + 1/2) of the additional cross webs are in the zone of said continuous thread portion and the remaining (z - 1/2) additional cross webs are located after the stream-dividing node following said continuous thread portion, as seen in the conveying direction.
 26. Screw machine according to claim 25, wherein at least one cross web is located in the zone of said continuous thread portion connecting the offset stream-dividing nodes.
 27. Screw machine according to claim 25, wherein at least one cross web is located between two stream-dividing nodes in the same screw channel.
 28. Screw machine according to claim 1, wherein said threads have bent portions at the stream-dividing nodes.
 29. Screw machine according to claim 28, wherein the outer edges of said longitudinal webs are spaced from the inner wall of said housing and the spacing therebetween being larger than the clearance of said threads with respect to the inner wall of said housing.
 30. Screw machine according to claim 29, wherein each of said one respective cross web and longitudinal web constitutes the stream-dividing node by forming an angle therebetween with a common vertex.
 31. Screw machine according to claim 30, wherein the stream-dividing nodes of adjacent screw channels are offset with respect to each other in the conveying direction of said screw shaft means.
 32. Screw machine according to claim 31, wherein an end portion of a cross web of one stream-dividing node is operatively connected, by means of a continuous thread portion, to a beginning portion of a longitudinal web of the stream-dividing node offset with respect thereto in the conveying direction in the adjacent screw channel.
 33. Screw machine according to claim 32, wherein at least one cross web is located in the zone of said continuous thread portion connecting the offset stream-dividing nodes.
 34. Screw machine according to claim 31, wherein at least one cross web is located between two stream-dividing nodes in the same screw channel.
 35. Screw machine according to claim 31, wherein an even number n of threads is provided and the stream-dividing nodes are arranged in parallel groups respectively arranged on a common cross-sectional plane.
 36. Screw machine according to claim 1, wherein said longitudinal webs and said cross webs are provided with a substantially flat ascending slope of between about 15* to 30*.
 37. Screw machine according to claim 36, wherein the outer edges of said longitudinal webs are spaced from the inner wall of said housing and the spacing therebetween being larger than the clearance of said threads with respect to the inner wall of said housing.
 38. Screw machine according to claim 37, wherein respectively one of said cross webs and one of said longitudinal webs form an angle therebetween and have a common vertex thereby constituting the stream-dividing node.
 39. Screw machine according to claim 38, wherein the stream-dividing nodes of adjacent screw channels are offset with respect to each other in the conveying direction of said screw shaft means.
 40. Screw machine according to claim 39, wherein an end portion of a cross web of one stream-dividing node is operatively connected, by means of a continuous thread portion, to a beginning portion of a longitudinal web of the stream-dividing node offset with respect thereto in the conveying direction in the adjacent screw channel.
 41. Screw machine according to claim 40, wherein at least one cross web is located in the zone of said continuous thread portion connecting the offset stream-dividing nodes.
 42. Screw maChine according to claim 38, wherein at least one cross web is located between two stream-dividing nodes in the same screw channel.
 43. Screw machine according to claim 39, wherein n number of threads are provided at said screw shaft means, and n-1 additional cross webs are provided in the zone of said continuous thread portion connecting two stream-dividing nodes offset in the conveying direction and related to adjacent screw channels.
 44. Screw machine according to claim 37, wherein said threads have bent portions at the stream-dividing nodes. 